Fire Extinguishers
Fire extinguisher types, colour codes, and correct usage per BS 5306. Know which extinguisher for which fire class.
Fire Classes
Fires are classified according to the type of fuel involved. Using the wrong extinguisher on a fire can be ineffective or dangerous.
| Class | Fuel Type | Examples |
|---|---|---|
| Class A | Solid combustible materials | Wood, paper, textiles, cardboard, plastics |
| Class B | Flammable liquids | Petrol, diesel, oil, solvents, paint |
| Class C | Flammable gases | Propane, butane, natural gas, methane |
| Class D | Combustible metals | Magnesium, aluminium, sodium, potassium |
| Electrical | Electrical equipment fires | Switchgear, distribution boards, motors, appliances. Not a class — isolate supply first, then treat as the underlying fuel class. |
| Class F | Cooking oils and fats | Deep fat fryers, cooking oils. Very high temperatures. |
Extinguisher Types and Colour Codes
All fire extinguishers in the UK have a red body (to BS EN 3). The colour band identifies the extinguishing agent. Know these for the ECS assessment.
Water
Colour band: All Red (no band)
Works by: Cooling the fire below ignition temperature.
Use on: Class A only.
NEVER use on electrical, oil/fat, or flammable liquid fires.
Foam (AFFF)
Colour band: Cream
Works by: Smothering and sealing the surface; also cools.
Use on: Class A and Class B.
Do not use on electrical fires (unless dielectrically tested). Not suitable for chip pan fires.
CO2 (Carbon Dioxide)
Colour band: Black
Works by: Displacing oxygen and cooling. Leaves no residue.
Use on: Electrical fires and Class B.
Risk of re-ignition. Hold horn by insulated handle only (frost risk). Not effective outdoors.
Dry Powder
Colour band: Blue
Works by: Chemical inhibition of the fire chain reaction.
Use on: Class A, B, C, and electrical.
Do not use in enclosed spaces (breathing hazard). Reduces visibility. Does not cool — risk of re-ignition.
Wet Chemical
Colour band: Yellow
Works by: Saponification — reacts with oil to form a soap-like seal. Also cools.
Use on: Class F (cooking oils/fats). Also effective on Class A.
The ONLY extinguisher suitable for deep fat fryer fires.
Extinguisher Suitability Matrix
This table shows which extinguisher types are safe and effective for each fire class. This is a key topic in the ECS HS&E assessment.
| Extinguisher | Class A Solids | Class B Liquids | Class C Gases | Electrical | Class F Cooking |
|---|---|---|---|---|---|
| Water (Red) | ✓ | ✗ | ✗ | ✗ | ✗ |
| Foam (Cream) | ✓ | ✓ | ✗ | ✗ | ✗ |
| CO2 (Black) | ✗ | ✓ | ✗ | ✓ | ✗ |
| Dry Powder (Blue) | ✓ | ✓ | ✓ | ✓ | ✗ |
| Wet Chemical (Yellow) | ✓ | ✗ | ✗ | ✗ | ✓ |
When to Use a Fire Extinguisher
Only attempt to fight a fire if ALL of the following conditions are met:
- The fire alarm has been raised and the fire service called
- You have a clear escape route behind you
- The fire is small and in its early stages
- You have the correct type of extinguisher
- You have been trained to use the extinguisher
- There is no risk to your personal safety
If in doubt, get out
Your safety always comes first. If the fire is too large, spreading rapidly, or you are unsure which extinguisher to use, evacuate immediately and wait for the fire service.
PASS Technique
Remember the PASS acronym when operating a fire extinguisher:
- P — Pull the pin (break the tamper seal)
- A — Aim at the base of the fire (not the flames)
- S — Squeeze the handle to release the extinguishing agent
- S — Sweep from side to side across the base of the fire
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